1. Field of the Invention
The present invention generally relates to trim panels used to cover the interior surfaces of a vehicle. The invention more particularly relates to panels used to cover the interior surfaces of a passenger vehicle where sound attenuation is desired. The invention most particularly relates to panels which are used in passenger vehicles where appearance and sound attenuation are required. Such panels are employed as the head liners, wall liners and carpets of a vehicle for the purpose of improving appearance, temperature and sound control while enhancing the passengers"" driving pleasure.
2. Description of the Prior Art
The use of trim panels and carpet panels to provide passenger comfort are well known in the art. For example, see U.S. Pat. Nos. 4,741,945; 4,508,774; and 5,334,338. In addition, the use of these known manufacturing techniques employed by the present invention for producing standard floor covering is also known. See U.S. Pat. No. 5,855,981.
Early efforts at sound attenuation in vehicles generally relied upon heavy, dense materials which would resist the entry of exterior noises into the passenger cabin. However, experience with such materials led to concerns about the transmission of vehicle vibrations and other sounds based upon the heavy insulating materials. Accordingly, the art has recently considered the use of ultralight, multifunctional, sound-insulating materials. For example, see WO 98/18656 and WO 98/18657.
More recently, it has been determined that ultralight, multifunctional, sound-insulating materials may not achieve their full benefit when used with exterior cover materials that do not compliment their function. Accordingly, the art desired an exterior or decorative cover material which permitted controlled sound transmission to the interior of the vehicle. It has been theorized that permitting transmission of some sound into the cabin will result in sound cancellation and a more pleasing passenger environment. As a result of the more pleasing environment, the use of ultralight materials will be greatly enhanced and a reduction in vehicle weight will be recognized without any decrease in cabin comfort.
The present invention provides a sound insulating structure cover panel that compliments the sound attenuation material. The method of manufacturing the panel comprises the steps of providing a laminated blank having an interior face which will be observable from the passenger compartment. The side opposite the interior face of the blank has a generally non-permeable polymeric layer adjacent to a primary backing and a secondary backing layer overlying the polymeric layer. In the preferred process, the previously described blank is elevated to a desired temperature and positioned in a closed forming mold such that the perimeter of the blank is retained in a fixed position. The forming mold is closed with a controlled pressure that is sufficient to expand the blank, conform it to the mold and render a panel having a desired permeable. Preferably, the post formation panel has a permeability of 500 rayls or less as measured on concentric airflow resistance equipment (C.A.R.E. unit) available from Rieter Automotive North America, Inc. 38555 Hills Tech Drive, Farmington Hills, Mich. 48331.